Arlene Arkinson was last seen with convicted child killer Robert Howard, who died in prison last year

A long-delayed inquest into the death of murdered schoolgirl Arlene Arkinson has finally started today, nine years after it was ordered.

The 15-year-old from Castlederg, Co Tyrone, vanished after a night out at a disco in Co Donegal in 1994.

Speaking outside the Laganside court complex, Kathleen Arkinson described her sister as a "blue-eyed girl".

Choking back tears, she said: "Mummy passed away when Arlene was 11 and Arlene was just the blue-eyed girl of the family. She was brilliant at art, she was good at school. I want people to know the real Arlene. She was our sister and she deserves to be found."

Ms Arkinson added that she hoped the long awaited inquest would help "ease" the family's pain.

Arlene Arkinson was last seen with convicted child killer Robert Howard, who died in prison last year.

Howard was acquitted of the teenager's murder by a jury that was unaware of his previous conviction for murdering schoolgirl Hannah Williams, 14, in south London.

He always remained the police's prime suspect in the Arkinson case.

The inquest process has been plagued by hold-ups, many due to the length of time police have taken to disclose classified papers to the court.

Not all documents have been handed over and last week it emerged that a government minister has signed off on a bid to withhold some top-secret files amid apparent concerns they could harm the public interest.

Northern Ireland Office minister Ben Wallace has approved the Public Interest Immunity (PII) application. The final decision on whether it will be granted rests with the coroner, Brian Sherrard.

Grounds for PII include matters of national security or the protection of police methodologies such as the use of informers.

While the government has obtained such immunity on sensitive papers relating to legacy terrorist cases in the north, lawyers for the Arkinson family have questioned why PII issues would be at play at the inquest into the death of a missing schoolgirl.

Mr Sherrard is set to hear legal submissions on the PII application on Tuesday, with at least part of the hearing due to be held behind closed doors.

On the opening day of the hearing the broad facts of the case will be set out, with Arlene's sister Kathleen to make a statement to court.

Howard, 71, had also been due to give evidence before the inquest. He died at HMP Frankland in Co Durham last October.

The inquest is being heard without a jury, with proceedings streamed to Omagh courthouse in Co Tyrone for the missing teenager's family.